Sterols and more specifically cholesterol are compounds present in animal fats entering into the composition of many foodstuffs, among which butter.
Now it has long been established that high blood levels of cholesterol (cholesterol LDL) are in direct correlation with serious cardio-vascular diseases.
The principal among them is atherosclerosis which is manifested by alteration in the wall of the arteries and of which one of the causes is the localized, excessive and abnormal deposit of cholesterol on the inner surface of the wall of an artery. The atheroma so formed can have tragic consequences like myocardial infarction. By way of illustration, it can be indicated that a reduction of 1% of the total blood cholesterol results in a reduction of 2% in the coronary risk. The excess cholesterol can also be the cause of gallstones.
Prevention remains one of the most effective means for remedying these disorders. It consists of reducing as much as possible the ingestion of cholesterol-rich foods or also of consuming food stuffs with a reduced content of cholesterol.
The concern of foodstuff industries is hence to remove cholesterol from products such as animal fats.
Thus, there have already been proposed various methods of extracting sterols from fats.
One of them consists of placing the animal fat in contact with digitonin which has the property of reacting with the cholesterol to give a precipitate. The performance and results of this method are not satisfactory due to the fact of the difficulty of separation of the precipitate from the medium. This method is, in any event, inapplicable industrially, especially for foodstuffs.
The cholesterol can also be extracted from fats by removal by means of a solvent. The main drawback of this process is that the solvents generally employed are toxic and there always remain traces in the fats concerned.
Microdistillation processes are also known, inapplicable on the industrial scale, as well as adsorption processes on columns as described, for example, in European patent application EP No. 0174848 and EP No. 0318326. These applications teach a process according to which the fat kept in the liquid state passes through an adsorbent column, in the event activated charcoal. It is clear that such a process is very laborious to employ and moreover the extraction that it permits is not very selective.
Another physico-chemical process of extraction of cholesterol from fats is disclosed by the Japanese patent application JP No. 59-140299. It consists of contacting a dry substance charged with cholesterol such as powdered milk, with supercritical CO.sub.2 at a temperature comprised between 35.degree. and 45.degree. C. and at a pressure comprised between 130 and 200 atm. The obtaining of these physical conditions necessitates the use of complex and cumbersome equipment. The conducting of the process is thus very delicate. Moreover, as is specified in the patent application, other lipid compounds are entrained by the super critical CO.sub.2. This process is hence not selective.
To remove sterols from fats, there has also been contemplated a process of bio-degradation of said sterols disclosed by patent application EP No. 0278794 and employing bacteria which, contacted with the fat, are adapted to metabolise at least one of the sterols that it contains. Like all processes bringing fermentation into play, this bio-degradation process is very delicate to conduct due to the fact of the variability inherent in living matter. In addition, the equipment employed, and the relatively long duration are, among other things, elements which render such a process laborious. Finally, the catabolites produced during these fermentations remain until now totally unknown as regards their nature and their toxicity and are, in any case, present in the fat so treated.
Through European patent application EP No. 0256911 a process for elimination of the cholesterol contained in a fat of animal origin is also known. It is based on the property already disclosed of cyclodextrins (cyclic polyglucoses of frustoconic tubular conformation with 6, 7 or 8 glucose units and denoted respectively by alpha, beta or gamma cyclodextrin) of receiving in their hydrophobic central cavity molecules of sterols and especially of cholesterol, to form inclusion complexes soluble in water. According to this process, the fat kept fluid id contacted with a cyclodextrin with stirring for 30 minutes to 10 hours so as to enable the formation of complexes. The separation of the latter is then effected by introduction of water into the reaction medium, which solubilises these complexes. The aqueous solution so obtained is then collected after decantation.
The extraction yield of the cholesterol by this process is hardly considerable. In the best cases, it is only 41%, and this after three successive extractions as is indicated in Examples 3 of the description of this European patent application.
Apart from these scarcely satisfactory performances, this process constitutes a succession of additional steps in the manufacture of a foodstuff. In fact, the procedure if it was adopted, for example in the case of butter, would necessitate firstly manufacturing the fat-based product, in an anhydrous form, subjecting it to the extraction treatment of the cholesterol, then of bringing it into its form of finished foodstuff, that is to say reconstituted butter. This process would necessarily hence be expensive in time, in equipment and in energy. Moreover, is is to be noted that according to this process the fat must be kept melted under an oxygen-free atmosphere. These technical characteristics involve resorting to a specific apparatus for maintaining the temperature and the supply of neutral gas. Lastly, the duration necessary solely for the first phase of complexation is at the minimum 30 minutes and in reality from 2 to 3 hours as indicated in the examples.
It emerges from the foregoing that none of the prior art solutions has permitted until now the production of food fats impoverished in sterols particularly in cholesterol-satisfactorily, that is to say responding to the industrial conditions of economic profitability, of flexibility of use, and of the quality of the final product.